Apparatus and method for cathode stripping

ABSTRACT

Disclosed is apparatus and a method for stripping electrodeposits from cathode blanks which apparatus comprises a conveyor for conveying cathodes to a stripping station, a stripping mechanism for stripping electrodeposits from the cathode blanks, quenching devices in the stripping station, a control device for controlling the quenching device so that quenching commences after the stripping mechanism engages the electrodeposit but before the stripping mechanism is activated, and conveyors for conveying stripped electrodeposits and cathode blanks from the stripping station.

United States Patent 1 1 3,883,403

Ettel et a1. 1 1 May 13, 1975 [541 APPARATUS AND METHOD FOR 3,779,87212/1973 Bomberger 204/12 CATHODESTRIPHNG FOREIGN PATENTS on APPLICATIONS[75] Inventors: Victor Alexander Ettel, Mississauga, 4 499 1 35 UnitedKingdom M 204 9 Ontario; Christopher Charles Dunkley, Sudbury, Ontario;Jose Antonio Blanco, Welland, Ontario; Robert Ray Matthews, Lively,Ontario, all of Canada [73] Assignee: The International Nickel Company,

Inc., New York, N.Y.

[22] Filed: Oct. 4, 1973 21 Appl. No.: 403,466

OTHER PUBLlCATlONS Metal Finishing, February 1956, pgs. 52-56.Electronics, September 1 1, 1959, p'gs. 1 14-1 17.

Primary Examiner-T. M. Tufariello Attorney, Agent, or Firm-M. W. Leff;E. C. MacQueen [57] ABSTRACT Disclosed is apparatus and a method forstripping electrodeposits from cathode blanks which apparatus comprisesa conveyor for conveying cathodes to a stripping station, a strippingmechanism for stripping electrodeposits from the cathode blanks,quenching devices in the stripping station, a control device forcontrolling the quenching device so that quenching commences after thestripping mechanism engages the electrodeposit but before the strippingmechanism is activated, and conveyors for conveying strippedelectrodeposits and cathode blanks from the stripping station.

14 Claims, 3 Drawing Figures APPARATUS AND METHOD FOR CATHODE STRIPPINGThe present invention pertains to apparatus and a method for strippingmetallic electrodeposits from cathode blanks.

Electrorefming and clectrowinning processes. particularly theelectrorefining of nickel and copper, conventionally involve the use ofa starting sheet upon which the metal being refined or recovered iselectrodeposited, which processes are known as multiple processes. Themultiple process includes, using copper as an example, electrodepositionof copper on a rigid mother blank that is coated with a partingcompound, stripping the electrodeposit from the mother blank.straightening the electrodeposit and attaching copper loops, which arecut up electrodeposits, to the straightened electrodeposit to formstarting sheets. The frail nature of these starting sheets can createproblems during elcctrorefining by warping, thereby causing shortcircuiting. Warped sheets must be withdrawn from the electro-refiningtank and straightened before being reintroduced into the electrolytictank. All of these operations involve a great deal of manual labor andare not readily automated.

It has frequently been suggested to employ robust cathode blanks uponwhich a heavy electrodeposit product, that can be mechanically strippedfrom the cathode blank, is directly formed. The working surface, i.e.,the surface upon which the electrodeposit is formed, can be made ofstainless steel, titanium or any other metal or alloy that is corrosionresistant under the electrolyte condition employed and that can bereadily surface finished to facilitate stripping of electrodepos its.

One of the major problems encountered in commercially implementingdirect electrodeposition is that mechanical stripping, whether or not aparting compound is employed, frequently involves rolling. hammering,chipping or chiscling to part the electrodeposit from the cathode blankso that the electrodeposit can be stripped from the blank by pullingwith mechanical means, Parting by rolling, hammering, chipping orchiseling damages the working surface, making subsequent parting evenmore difficult. When such mechanical parting is employed, the workingsurfaces must be frequently refinished thereby reducing some ofthesavings provided by the direct process.

Generally speaking, the present invention contemplates an improvedmethod and apparatus for stripping cathodes, which comprise a cathodeblank and an electrodeposit on the cathode blank. The apparatus includesa stripping station, a conveyor for conveying cathodes to the strippingstation, an indexing device for placing the cathode into position in thestripping station, a conveyor for conveying the cathode blank from thestripping station and a conveyor for conveying stripped electrodepositfrom the stripping station. The improvement comprises equipping thestripping station with support means for supporting a cathode, grippingmeans for gripping the electrodeposit, thermal means for rapidlyaltering the temperature of the electrodeposit to thermally part theelectrodeposit from the cathode blank. control means for activating thethermal means only after the gripping means have engaged theelectrodeposit and for deactivating the thermal means after theelectrodeposit is at least partially parted from the cathode blank andstripping means affixed to the gripping means for stripping the partedelectrodeposit from the cathode blank.

FIG. I is a schematic top view of automatic cathode stripping apparatusshowing portions of conveyor assemblies and a washing station and astripping station that includes the improvements in accordance with thepresent invention;

FIG. 2 is a vertical section of the stripping station taken along theline 2-2 in FIG. I; and

FIG. 3 is a vertical section of the stripping station taken along theline 3-3 in FIG. 1.

Referring now to the drawings, there is depicted in the Figuresapparatus for stripping cathodes including a conveyor A, strippingstation B, conveyor C, con veyor D and washing station E,

The cathodes comprise a cathode blank I2 and an electrodeposit 14 on thecathode blank. Electrodeposit 14 is sufficiently heavy, e.g., at leastabout onesixteenth inch, and advantageously between about oneeighth inchand one-half inch, to withstand the forces it is subjected to during thestripping operation. The cathode blank 12 comprises a plate ofa metalselected from the group consisting of wrought copper, alumi num,stainless steel and titanium having a working surface roughness of fromabout 5 to 250 microinches RMS, e.g., between about and 200 microinchesRMS, and having electrically insulating masking means at at least theside edges thereof to minimize electrodeposits at and envelopment aroundthe edges. The working surface of the cathode blank can be coated orprovided with a film of a parting compound to facilitate parting.Examples of parting compounds are oil, metallic soaps, grease, stearatesand resins, such as sodium resinate.

Stripping of eleetrodeposits from cathode blanks can be improved byemploying cathode blank materials that have a substantially differentcoefficient of thermal expansion than the material beingelectrodeposited. For example, when electrodepositing copper, which hasa coefficient of thermal expansion of l6.8 X 10*" (defined as change inlinear dimension per unit length per degree Celsius), a titanium cathodeblank, which has a coefficient of thermal expansion of 9.0 X 10*, isemployed. In most instances, it is advantageous for the cathode blankand the electrodeposit to have a minimum difference in their coefficientof thermal expansion of at least about 10 percent, eg, preferably atleast about 25 percent. When cathode blanks and electrodeposits havingsuch minimum differences in coefficients of thermal expansion are cooledor heated from electrodeposition temperatures, stresses are induced atthe electrodeposit-cathode blank interface which promote parting.

Partial parting of the electrodeposit from the cathode blank can also bepromoted by adding a stress inducing reagent to the electrolyte whichcontains soluble salts of the non-ferrous metal being depositedv Forexample, when electrodepositing copper, small but effective amounts ofat least one stress-inducing reagent selected from the group consistingof guar gum, gelatine, benzotriazole, thiourea, animal glue, andpolyacrylamide are added to the electrolyte. When electrodepositingnickel, stress-changing reagents including ethylenecyanohydrine,chloride ion, butynediol, naphthalene sulfonic acids, and saccharin areadded to the nickel-containing electrolyte in small but effectiveamounts to change internal stresses in the electrodeposit so that uponcooling or heating from the electrodeposition temperature parting fromthe cathode blank is promoted. In most instances. stress-inducingreagents are added to the electrolyte in amounts of at least about 0.0lparts per million (ppm). and advantageously in amounts between about 0.]ppm and 50 ppm (in some instances amounts up to about 100 ppm can beused), in order to insure the imparting of internal stresses to theelectrodeposit while minimizing contamination of the electrodeposit bythe additive.

Cathodes are removed from the electrolytic cell, not shown on thedrawings, and are conveyed by conveyor A to stripping station B whereindividual cathodes are placed in stripping position by indexingmechanism 16. Conveyor A can be equipped with heating means, such as ahot air blower or hot water spray, to maintain cathodes held therein atpredetermined temperatures to minimize the problems associated withpremature parting and possible stripping within the conveyor.

Stripping station B comprises links pivotally mounted on crankshaft 22and equipped with suction pads 24 for gripping electrodeposit 14. Links20 can be hollow so that pumps 26 can evacuate suction pads 24. Suctionpads 24 are sufficiently large so that the pressure differential betweenatmospheric pressure and the subatmospheric pressure within the padsmultiplied by the total area of all the cups engaging one side of thecathodeis greater than the forces required to pull electrodepo t 14 fromcathode blank 12. Links 20 are moved from the starting position, asshown by the solid lines in FIG. 2 to the electrodeposit engagingposition, as shown by the phantom lines in FIG. 2, by air motors 28,only one being shown in FIG. 2 for the sake of clarity, via linkages 30and 32. Stripping station B is also equipped with a plurality of nozzles34 for rapidly quenching or heating electrodeposits 14 for thermallyparting the electrodeposit from cathode blank 12. Water or otherquenchants are led to nozzles 34 via pipes 36 and the flow of water orother quenchant to and through pipes 36 and nozzles 34 is controlled bycontrol mechanism 38 which can be a relay-operated valve. Once suctionpads 24 have engaged and gripped electrodeposit 14, control mechanism 38is activated and water flows through pipe 36 and nozzles 34 to rapidlyquench and thermally part the electrodeposit from cathode blank 12.After electrodeposit 14 is parted from at least the tip of the cathodeblank 12, air motor 28 is actuated to rotate linkages 20 from thevertical to the horizontal position thereby stripping the electrodepositfrom the cathode blank.

Stripped cathode blanks 12 are removed from stripping station 8 byindexing mechanism I6 to conveyor C which conveys the cathode blanksback to the electrolytic tanks or to a reconditioning area to beprepared for further use.

Stripped electrodeposits 14 are transferred to washing station E byconveyor C. Upon exiting the washing station, the strippedelectrodeposits can be melted or otherwise formed into commercialshapes.

In operation. cathode blanks having a copper electrodeposit 14 thereonare removed from an electrolytic tank at a temperature between about 60and 70C., dipped in a tank of hot water at a temperature about 60C. andplaced on conveyor A. The hot cathodes are conveyed by conveyor A tostripping station B without substantially altering their temperaturesand are placed therein by indexing mechanism 16 at temperatures betweenabout 50 and 65C. Suction pads 24 engage electrodeposit l4, and onlythen is control mechanism 38, which can be a relay actuated by a timeror by means for sensing that a vacuum has been established within thesuction pads, activated to commence quenching to lower the temperatureof the electrodeposit 14 to less than about 40C. When the cathode isquenched, electrodeposit 14 parts from cathode blank 12 and links 20 areactuated to pull the parted electrodeposit from the cathode blank. Thestripped electrodeposits are placed on conveyor C by links 20 and areconveyed thereby to working station E. The stripped cathode blank isplaced on conveyor D by indexing mechanism 16 and is conveyed back tothe electrolytic tank.

If for any reason the automatic stripping operation must be temporarilystopped, cathodes on conveyor A should be maintained at a temperaturenot materially different from the cathodes emerging from theelectrolytic tanks, e.g., above C., in order to prevent prematurestripping, either on conveyor A or in stripping station B, or should beremoved from conveyor A. The cathodes can be maintained at temperatureduring such temporary stoppages by contacting the cathodes with eitherhot air, water or steam or placing them into the hot water tank.

In order to give those skilled in the art a better appreciation of thepresent invention the following illustrative example is given:

A cathode comprising a cathode blank of titanium polished to 60microinches RMS and an electrodeposit of copper of 0.3 inch while wetand at a temperature of C. was placed into position in the strippingstation by an indexing mechanism as shown in FIG. 2. Rectangular vacuumcups having interior cavities measuring 3.5 inches by 7 inches weremoved into engaging position by air motor drawn linkages and thecavities were evacuated to 2.4 psi to grip the electrodeposits with aforce of 300 pounds. Once the vacuum cups were gripping theelectrodeposits, quenching means were activated to lower the temperatureto 28C., at which point separation of the upper part of theelectrodeposit from the titanium blank was visible and the quenching wasthen terminated. The linkages holding the vacuum cups were then moved tothe horizontal from the vertical position to strip the electrodepositfrom the cathode blank. After stripping, the vacuum was released and thestripped electrodeposits were conveyed to a washing station. Thestripped cathode blank was removed from the stripping station to aconveyor to be returned to the electrolytic cell, and the strippingstation was ready to receive another cathode for stripping.

Although the invention has been described primarily by reference to theapparatus, it will be observed that the invention also includes a methodfor electrodepositing a non-ferrous metal, e.g., copper, nickel, cobalt,zinc and manganese, on a cathode blank and subsequently stripping theelectrodeposit from the cathode blank. The method compriseselectrodepositing a nonferrous metal on a cathode blank in anelectrolytic cell containing an electrolyte that is maintained at apredetermined temperature to form a cathode comprising the cathode blankand an electrodeposit of a preselected thickness thereon. removing thecathode from the electrolytic cell, conveying the cathode to a strippingstation while maintaining the temperature of the cathode atsubstantially the predetermined temperature to minimize prematureparting, engaging the electrodeposit in the stripping station withgripping means affixed to stripping means, rapidly altering thetemperature of the engaged electrodeposit to part at least partially theelectrodeposit from the cathode blank and then actuating the strippingmeans to strip the parted electrodeposit from the cathode blank.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are consid ered to bewithin the purview and scope of the invention and appended claims.

We claim:

1. In an apparatus for stripping cathodes, the cathode comprising acathode blank and a metallic electrodeposit on the cathode blank, saidelectrodeposit having been applied at an electrodeposit bathtemperature, which apparatus includes a stripping station, means forconveying cathodes to the stripping station, means for indexing thecathode in and for removing the cathode blank from the strippingstation, means for conveying the cathode blank from the strippingstation and means for conveying stripped electrodeposit from thestripping station, the improvement which comprises support means in thestripping station for supporting the cath ode, gripping means in thestripping station for gripping the electrodeposit, thermal means formaintaining the temperature of the electrodeposit substantially at thebath temperature until the gripping means have engaged the cathode inthe stripping station, thermal means for rapidly altering thetemperature of the electrodeposit after the gripping means have engagedthe electrodeposit to thermally part the electrodeposit from the cathodeblank, control means for activating the thermal means only after thegripping means have engaged the electrodeposit and for deactivating thethermal means after the electrodeposit is parted from the cathode blankand stripping means affixed to the gripping means for stripping theparted electrodeposit from the cathode blank,

2. The apparatus described in claim 1 wherein the gripping means aresuction pads.

3. The apparatus described in claim I wherein the thermal means includesat least one nozzle directed at the electrodeposit, a quenchant sourceand means for conveying quenchant from the source to the nozzle forrapidly lowering the temperature of the electrodeposit.

4. A process for electrodepositing a non-ferrous metal on a cathodeblank and subsequently stripping the electrodeposit from the cathodeblank which comprises electrodepositing a non-ferrous metal on a cathodeblank in an electrolytic cell, said cathode blank and electrodeposithaving different coefficients of thermal expansion, and saidelectrolytic cell containing an electrolyte that is maintained at apredetermined temperature, to form a cathode comprising the cathodeblank and an electrodeposit of a preselected thickness thereon of atleast about one-sixteenth inch thickness, removing the cathode from theelectrolytic cell, conveying the cathode to a stripping station whilemaintaining the temperature of the cathode at substantially thepredetermined temperature to minimize premature parting, engaging theelectrodeposit in the stripping station with gripping means affixed tomechanical stripping means, rapidly altering the temperature of theengaged electrodeposit to part at least partially the electrodepositfrom the cathode blank at an edge and then actuating the stripping meansto strip the parted electrodeposit from the cathode blank.

5. The process described in claim 4 wherein the nonferrous metal is atleast one member selected from the group consisting of copper, nickel,cobalt, zinc and manganese.

6. The process as described in claim 4 wherein the cathode blank and theelectrodeposit have a minimum difference in their coefficients ofthermal expansion of at least about 10 percent.

7. The process as described in claim 6 wherein the cathode blank is madeof a metal selected from the group consisting of wrought copper,aluminum, stainless steel, or titanium.

8. The process as described in claim 6 wherein the working surface ofthe cathode blank is coated with a parting compound.

9. The process as described in claim 6 wherein the parting compound isat least one member selected from the group consisting of oil, metallicsoaps, grease, stearates and resins.

10. The process as described in claim 4 wherein the electrolyte containsa stress-inducing reagent in small but effective amounts to induceinternal stresses in the electrodeposit to promote parting.

11. The process as described in claim 4 wherein the non-ferrous metal iscopper, the electrolyte contains copper salts and a stress-inducingreagent in small but effective amounts to induce internal stresses inthe electrodeposit and heated to a temperature between about 60 and C.,the cathode blank is made of a metal selected from the group consistingof wrought copper, stainless steel and titanium and its working surfaceis coated with a parting compound and the electrodeposit is quenchedwith water to lower its temperature to less than about 40C. to promoteparting.

12. The process as described in claim 4 wherein the non-ferrous metal isnickel, the electrolyte contains nickel salts and a stress-inducingreagent in small but efi'ective amounts to induce internal stresses inthe electrodeposit and heated to a temperature between about 60 and70C., the cathode blank is made of a metal selected from the groupconsisting of wrought nickel, aluminum, stainless steel and titanium andits working surface is coated with a parting compound and theelectrodeposit is quenched with water to lower its temperature to lessthan about 40C. to promote partmg.

13. The process as described in claim 4 wherein the non-ferrous metal isnickel, the electrolyte contains nickel salts and is heated to atemperature between about 60 and 70C., the cathode blank is made of ametal selected from the group consisting of wrought nickel, aluminum,stainless steel and titanium and the electrodeposit is quenched withwater to lower its temperature to less than about 40C. to promoteparting.

14. The process described in claim 7 wherein the cathode blank has aworking surface roughness of from about 5 to about 250 microinches RMSv

1. In an apparatus for stripping cathodes, the cathode comprising acathode blank and a metallic electrodeposit on the cathode blank, saidelectrodeposit having been applied at an electrodeposit bathtemperature, which apparatus includes a stripping station, means forconveying cathodes to the stripping station, means for indexing thecathode in and for removing the cathode blank from the strippingstation, means for conveying the cathode blank from the strippingstation and means for conveying stripped electrodeposit from thestripping station, the improvement which comprises support means in thestripping station for supporting the cathode, gripping means in thestripping station for gripping the electrodeposit, thermal means formaintaining the temperature of the electrodeposit substantially at thebath temperature until the gripping means have engaged the cathode inthe stripping station, thermal means for rapidly altering thetemperature of the electrodeposit after the gripping means have engagedthe electrodeposit to thermally part the electrodeposit from the cathodeblank, control means for activating the thermal means only after thegripping means have engaged the electrodeposit and for deactivating thethermal means after the electrodeposit is parted from the cathode blankand stripping means affixed to the gripping means for stripping theparted electrodeposit from the cathode blank.
 2. The apparatus describedin claim 1 wherein the gripping means are suction pads.
 3. The apparatusdescribed in claim 1 wherein the thermal means includes at least onenozzle directed at the electrodeposit, a quenchant source and means forconveying quenchant from the source to the nozzle for rapidly loweringthe temperature of the electrodeposit.
 4. A PROCESS FORELECTRODEPOSITING A NON-FERROUS METAL ON A CATHODE BLANK ANDSUBSEQUENTLY STRIPPING THE ELECTRODEPOSITING A FROM THE CATHODE BLANKWHICH COMPRISES ELECTRODEPOSITING A NON-FERROUS METAL ON A CATHODE BLANKIN AN ELECTROLYTIC CELL, SAID CATHODE BLANK AND ELECTRODEPOSIT HAVINGDIFFERENT COEFFICIENTS OF THERMAL EXPANSION, AND SAID ELECTROLYTIC CELLCONTAINING ELECTROLYTE THAT IS MAINTAINED AT A PREDETERMINEDTEMPERATURE, TO FORM A CATHODE COMPRISING THE CATHODE BLANK AND ANELECTRODEPOSIT OF PRESELECTED THICKNESS THEREON OF AT LEAST ABOUTONE-SIXTEENTH INCH THICKNESS, REMOVING THE CATHODE FROM THE ELECTROLYTICCELL, CONVEYING THE CATHODE TO A STRIPPING STATION WHILE MAINTAINING THETEMPERATURE OF THE CATHODE AT
 5. The process described in claim 4wherein the non-ferrous metal is at least one member selected from thegroup consisting of copper, nickel, cobalt, zinc and manganese.
 6. Theprocess as described in claim 4 wherein the cathode blank and theelectrodeposit have a minimum difference in their coefficients ofthermal expansion of at least about 10 percent.
 7. The process asdescribed in claim 6 wherein the cathode blank is made of a metalselected from the group consisting of wrought copper, aluminum,stainless steel, or titanium.
 8. The process as described in claim 6wherein the working surface of the cathode blank is coated with aparting compound.
 9. The process as described in claim 6 wherein theparting compound is at least one member selected from the groupconsisting of oil, metallic soaps, grease, stearates and resinS.
 10. Theprocess as described in claim 4 wherein the electrolyte contains astress-inducing reagent in small but effective amounts to induceinternal stresses in the electrodeposit to promote parting.
 11. Theprocess as described in claim 4 wherein the non-ferrous metal is copper,the electrolyte contains copper salts and a stress-inducing reagent insmall but effective amounts to induce internal stresses in theelectrodeposit and heated to a temperature between about 60* and 70*C.,the cathode blank is made of a metal selected from the group consistingof wrought copper, stainless steel and titanium and its working surfaceis coated with a parting compound and the electrodeposit is quenchedwith water to lower its temperature to less than about 40*C. to promoteparting.
 12. The process as described in claim 4 wherein the non-ferrousmetal is nickel, the electrolyte contains nickel salts and astress-inducing reagent in small but effective amounts to induceinternal stresses in the electrodeposit and heated to a temperaturebetween about 60* and 70*C., the cathode blank is made of a metalselected from the group consisting of wrought nickel, aluminum,stainless steel and titanium and its working surface is coated with aparting compound and the electrodeposit is quenched with water to lowerits temperature to less than about 40*C. to promote parting.
 13. Theprocess as described in claim 4 wherein the non-ferrous metal is nickel,the electrolyte contains nickel salts and is heated to a temperaturebetween about 60* and 70*C., the cathode blank is made of a metalselected from the group consisting of wrought nickel, aluminum,stainless steel and titanium and the electrodeposit is quenched withwater to lower its temperature to less than about 40*C. to promoteparting.
 14. The process described in claim 7 wherein the cathode blankhas a working surface roughness of from about 5 to about 250 microinchesRMS.